Manufacture of electric filaments.



UNITED STATES PATENT OFFICE.

CABIIAUER VON WELSBACH, OF VIENNA, AUSTRIA-HUNGABY, ASSIGNOR TO WELS- ZBAGH LIGHT COMPANY, OF GLOUCESTER CITY, NEW JERSEY, .A CORPORATION OF NEW JERSEY.

MANUFACTURE OF ELECTRIC FILAMENT S.

No Drawing.

Specification of Letters Patent.

Application filed August 9, 1898. Serial No. 588,207.

.- the following is a specification.

The present invention relates to a thin, hair-like thread or filament of metallic osmium, of a dense or compact structure or consistency, and adapted for use as the incandescentfilament in an electric lamp.

The object of the invention is to provide an osmium filament which shall have the;

qualities requisite for such an incandescent filament, and also-to provide a method .or process by which it can be readily manufactured on a commercial scale.

Heretofore, so far as I am aware, no method was known for producing osmium filaments of the kind referred to. It has long been known that osmium possessed. many characteristics which were of great value for the purpose; but it is a metal of such a peculiar character, and is so difiicult to obtain and treat, that attempts to utilize it in the manufacture of filaments have been attended with no success. I have succeeded in making osmium filaments and in devising several methods for producing them, in a commercial form, at a moderate cost.

I 'will describe one of the processes which may be followed in obtaining the article that I have produced.

I place a very thin latinum wire in a reducing atmosphere 0 the water gas class, that is to'say, one in which I have water vapor together with hydrocarbon, and I then subject the wire to heat, preferably by passing an electric current therethrough. I then introduce into the chamber containing such atmosphere, fumes or vapors from a volatile osmium compound, such as osmium tetroxid. Osmium is deposited upon the wire. But there are several conditions which must be complied with in taking these steps. The osmium is (even among those of its own group .of highly infusiblevmetals) characterlzed b its strong chemical afiinity for a number 0 other bodies, such as oxygen, etc. Therefore, in the reducing atmosphere,

.no free oxygen must be present. A hydrocarbon atmosphere would meet this partlcular requisite; but in turn would be subj ect to objections of its own, as for instance,

it would readily deposit carbon upon the osmium. Hence I employ an atmosphere of a mixture of hydrocarbon and water vapor as mutual correctives, the one to prevent the formation of oxids, and the other to avoid the deposit of carbon. Furthermore, I find it also'highly necessary that the osmium coat ing be deposited very slowly and very uniformly so that it shall be of the proper density and cross section at all points.

I deliver the osmium vapor intermittently or at intervals, preventing the saturating or surcharging of the reduction chamber, and allowing the volumes of vapor to readily disperse themselves throughout the region of thewire and permit a slow and Patented Nov. 22, 1910.

uniform deposit. The result is the formation of a layer. of uniform thickness of osmium or osmium compound which under the action of the heat is made coherent, dense and uniform. This stage of the process is carried on at a comparatively low tempera ture to prevent the formationof oxids, but, 'if too low, the OSIlllllllledBPOSltBd will contaln oxids of osmlum, which, however, are

not especially objectionable, as they are subsequently decomposed in the treatment which follows. I then .place the wire carrier or fillet and its coating in an atmosphere of reducing'gases such as the mixture of gases and vapors incident to the incomplete combustion of illuminating gas produced bythe ignition thereof at the base of the air feed openings of a Bunsen burner, the said mixture of gases (consisting of hydrogen, carbon monoxid, carbon dioxid and hydrocarbons and which also contains water vapor) and vapors being collected from the burner tube,'and I gradually increase the heat passing through the filament or wire finally carrying'it up to and above the temperature at which platinumvolatilizes.

.The osmium compounds, such as the lower oxids above referred to, are completely reduced. But the final, intensely high heat is such as to withdraw even from the alloy the greater part of the platinum which may have united with theosniium. At the high temperature, the osmium, especially when ina protecting atmosphere or in oacuo, has a should exceed the quantityof the platinum tendency to assume a partially fused or cinderlike condition, and it will not liquefy or volatilize even up to a temperature much higher than that at which the volatilization of platinum occurs. The effect of this high temperature is, furthermore, to drive out from the filament all or substantially all of the gases which would-otherwise be occluded therein.

As above stated, the layer must be dense and uniform, and these characteristics can be attained to the extent desired by slowly and uniformly, depositing the osmium in the way described by intermittently bringing "charges of the osmium vapor into the region of the wire, the deposit or layer thus being under The diameter of the filament is to be governed by the conditions presented in each case, but the end aimed at is to ultimately obtain a self-sustaining filament as th1n as possible to have proper resistance to the current, and yet thick enough to endure the necessary current and to withstand the unavoidable shocks and jars to which the lamp is subjected when in use;but the quantity of osmium'deposited upon the platinum wire as otherwise the filament will be destroyed by the melting of the platinum. Not only can these successive coatings or laminae of osmium thus be produced, but also by a 'modified method, to wit, by dipping the carrier or fillet in a suitable solution of an osmium compound and heating the fillet and its coatin after each dipping to the proper oint, an finally subjecting it to. higher and igher tem rature successively in the-man.- ne'r above de scribed.

From the article resulting from this treatment, the carrier or fillet being removed by v the action of the electric current, there will remain a self-supporting, hollow, threadlike or hair-like filament of osmium of the proper electrical resistance and with the required mechanical sustaining power. In

either case the coating becomes transformed into a unitary coherent, compact structure of such nature that there is no disintegration due ,to differences of expansion and contraction or from other causes.

' Instead of a platinum wire core there may be used other metals or alloys which are duetile enough to be formed into wire, which can withstand the temperature at which the oxids of osmium are deoxidized in reducing gases into metallic osmium.

The completed filament is to be mounted in a lamp bulb in vacuo or portective gas and is connected to the leading-in wires through the medium of an osmium cement therewith I \Vhat I claim is for an electric lamp,formed of metallic osmium arranged i'n a pluralityof vsuperimposed minute layers or laminae all rendered compact and coherent, substantially as set forth.

2. A flexible, elastic, incandescent filament for an electric lamp, formed of metallic osmium arranged in several superimposed selfsupporting layers or laminae formed into a unitary, compact structure, substantially as set forth. I

3. A flexible, elastic, incandescent filament for an electric lamp, consisting of a hollow or tube like thread of metallic osmium formed of osmium particles arranged in a plurality of superimposed minute layers or laminae rendered coherent and compact, substantially as set forth.

4. A flexible,'elastic, incandescent filament for an electric lamp, formed of metal infusible at the temperature at which platinum volatilizes and arranged in a plurality of superimposed minute layers or laminae all rendered compact and coherent, substantially as set forth.

5. The herein described process of forming an incandescent filament for an electric lamp, consisting in depositing upon a carrier or fillet wire of metal infusible at ordinary temperatures and fusible only at high temperatures, a coating of metallic osmium, and heating the said coating to form a coherent, condensed structure by the action of the electric current until it is brou ht to the temperature of volatilization of thecarrier or fillet metal, substantially as set forth.

6. The herein described process of making an incandescent filament for an electric lamp, consisting in depositing upon a carrier or fillet wire of metal infusible at ordinary temperatures and fusible only at high temperatures, a coating of osmium, then subjecting the osmium to the high heat of the electric current for the purpose of assuring the reduction to the metallic state of all-of the osmium present, and raising the heat generated by the current to the temperature of volatihzation of the carrier. or fillet, thus the temperature of volatilization of the fillet 125 -metal and thus finally leaving the filament 976,616 3 in a densecoherent form substantially as set compact and coherent, flexible, elastic filaforth. I ment by raisingit above said temperature,

8. The herein described process of forming substantially as set forth. an incandescent filament for an-electric lamp, Signed this 27th da of -J 111 1898.

-5 consisting in depositing intermittently upon CARL AUER ON LSBACH.

a fillet a series of layersof a metal infuslble, Witnesses: at the tem rature at which qlatinum vola- Lnnwm Han-men, tilizes, an uniting the severa layers into a ADOLF GALLIA. 

